Process for the manufacture of white lead.



F. H. SHARPE. PROCESS FOR THE MANUFACTURE OF, WHITE LEAD.

- APPLIOATION FILED SEPT. 3, 1912.

Patented Feb. 24. 191 i FREDERICK HERBERT SHAH-PE, OF COUNTY OF LANCASTER, ENGLAND.

PROCESS FOR, THE MANUFACTURE OF WHITE LEAD.

rosaaeo.

, Specification of Letters Patent.

Patented lFeb. 2st, 191 2:.

Application filed September 3, 1912. Serial No. 718,384.

To all whom it may concern Be it known that l, FREDERICK HERBERT Siinnrii, a. subject. of the King of Great Britain, residing in county of Lancaster, Eng land, and whose post-oilice address is The Ferns, Cressington Park, near Liverpool, in the county of Lancashire, England, chemist, have invented certain new and useful Imprmtancnts in Processes for the Manufacture of White Lead, of which the following is a specification.

There is considerable difliculty in the eco- DOIDlC production of white lead by the precipitation process. When suflicientacetic acid is used to dissolve completely the lead oxid, there is no dilliculty in making the product free from unconverted lead oxid, metallic lead and other foreign substances; but the loss, of acetic acid is COHSlClGlflblG and the handling of large quantities of liquid which is necessary in any precipitation process Working with complete dissolution, is detrimental to the process, and is avoided by my invention.

It is the object of the present invention to, produce white lead in a continuous operation, which serves, at the same time, to separate the white lead from the particles of metallic lead and lead oxid remaining uncarbonated, and from any foreign matter that may be present, such as, for example, higher oxids of lead, so that there is finally obtained a white lead product, which is marketable, without further treatment, except in so far as it may be mixed with oil, or separated from the liquor and dried. The operation may be conducted with a minimum of acetic acid, lead acetate, or other known agent, adapted to assist carbonation, such as nitric acid or common salt. By using a larger proportion of acetic acid, or other known agent, more carbon dioxid would be retained in passingthrough the apparatus.

acetic acid would entail the filtering and washing of the final product, in which case it would be advisable to retain the liquors from such filtering because the increased amount of acetic acid, or other agent, con tained therein, would render the throwing away of such liquors, a considerable addi tional expense.

Although an assisting agent is necessary in this process, as in known processes, for

a nd separating I t i but the presence of an increased quantity of.

in th as consisting in carbonating convenience I shall to the open-ition the lead oxid.

The method consists in simultaneously and continuously carbonating the lead oxid,

with the aid of the carbonating agent the basic carbonate. produced by a process resembling elutriation, that is to say a process in which particles to be separated from heavier or less bulky particles are carried to the surface of a liquid in which the particles are suspended and are removed by overflow ofliquid. This may be done by using a series of closed vessels connnunicatiug with r-ach other in such a manner that the carl'ionating gas or gases pass through the liquid in eachyessel, and at the same time the basic lead carbonate and the lead oxid undergoing carbonation are carried to the surface of the liquid in each vessel by the gas or gases passing through the liquid, and are carried forward from vessel to vessel as fresh liquid is admitted into the first of the series. In this manner higher oxids 'of lead and metallic lead are gradually separated by a process of separation resembling elutriation which occurs in each vessel;

The invention is illustrated in the accompanying drawing, which is a vertical section through an apparatus suitable for applying the method.

The apparatus comprises a mixing vat a, and a series ofclosed vessels 0, 0 (Z, preferably ofthe conical shape shown. The requisite proportions of lead. oXid, water and acetic acid, or other known agent, are mixed in vata, which is provided with a stirrer to prevent the oxid from sinking to the bottom. The mixture is then forced through pipe 6 b v.means of a steam. injector 6 into the vessel c. The rate of flow through pipe 5 is controlled by .means of cocks f. Any other suitable mode of introducing the requisite substances into the vessel 0 may of course be adopted. In vessel 0 the mixture is sub- .jected to the action of carbonic acid gas the mixture and facilitate the control of the carbonation. Another advantage in using specification refer res 1 g cerv oxidize any nne m tallic read in the mixture, producing oxid of lead which is thereupon carbonated. In this specification the gas or mixture of gases containing the carbonic acid is sometimes referred to as the ,carbonating agent. The mixture in vessel 0 is a itated and carbonated to a certain degree by the gases passing through it. The separation begins in this vessel; the oxid which is undergoing carbonation rising to the surface where the which are the nature of the oxid under treatment and the composition of the carbonating agent. I have found seven vessels a suitable number and the drawing. represents part of a plant, having four vessels of the form 0', c and three vessels oft-he form d. I have found that metallic lead may travel as far as the fourth vessel but there becomes oxidized and carbonated, so that after the fourth vessel separation is not of such importance and the remaining vessels (Z may be more nearly cylindrical in shape and of somewhat smaller dimensions so that the materials may be more fully agitated therei proportion in. The several vessels are preferably constructed of wood and the communicating pipes of copper.

It is preferable that the liquid in the vessel should be hot so as to produce a white lead as dense as possible. My process is particularly well adapted for use of hot liquor because being carried out in closed vessels and with a very small proportion of acetic acid there is no tendency" for more than a trace of acetic acid to evaporate, whereas in those processes in which a large of acetic acid is used and the vessel is open the loss of the acid becomes a serious source of expense. I may introduce a steam jet into the vessel 0 so as to raise the liquor to the boiling point, or the steam injector emay be used for this purpose.

vThe apparatus is particularly designed to' deal with lead oxids which are easily attacked by acetic acid or other agent for helping the canbonation; if other oxids are used the action is much slower.

sludge which may be accumulated in the carbonating vessels maybe removed by stopping. the operation of the apparatus for in a. position convenient a ot. a ,0 "J afuu aou a short time until the sludge has settled, whereupon it may be drawn off through a cool: 2' provided for the purpose.

Each vessel is fitted with a screw plug is for cleaning out pipe it when the plug hasbeen removed. A cock on the delivery-pipe of the last vessel serves to control the pressure under which the carbonation occurs.

Although separate vessels have here been described it will be obvious that a single vessel sub-divided into compartments may be used.

The proportion of acetic acid or. other agent used in my process depends on the proportion of water present in the mixture and the proportion of carbonic acid gas in the carbonating gases. \Vhen coke fumes are used as the source of carbonic acid gas I find that a suitable proportion of acetic acid is about 1 part to 4.00 parts of lead oxid and 1600 parts of water.

The white lead is delivered from the last of the vessels (Z into a suitable collecting vat wherein it is allowed to settle and the water run off. The white lead may be shoveled out to be dried or for mixing with oil, and inasmuch as the proportion of lead acetate in it is very small there is no necessity for filtering or washing it.

I claim- 1. Process for the manufacture of white lead which consists in suspending lead oxid in water containing an assisting agent, caus-' ing the suspension to iiow continuously into a vat, so that-liquid flows from the upper part of the vat, passing carbonating gas through the suspension in the vat and col lecting the white lead carried away by th liquid which flows from the vat.

2. Process for the manufacture of white lead, which process consists in suspending lead oxid in water containing an assisting agent, causing the suspension to flow continuously into the first of a series of compartments so that liquid flows from the upper part of this compartment and through each of the remaining compartments, passing carbonating gas through each compartment and collecting the white lead which is carried away from the last compartment by the liquid flowing therefrom..

3. Process for the manufacture of white lead, which process consists in mixing lead oxid with water containing an assisting agent, heating the mixture, causing the mixture to flow continuously into a vat, so that liquid flows from the upper part of the vat, passing carbonating gas through the .suspension in'the vat and collect-ing the white lead carried away by the liquid which flows from the vat.

4. Process for the manufacture of white lead, which process consists in mixing lead oxid with water containing an assisting flpartments, passing carbonating gas through each compartment and collecting the white lead which is carried away from the last compartment by the liquid \flowing therefrom.

5. Process for the manufacture of white lead which process consists in suspending lead oxid inwater containing acetic acid, causing the suspension to flow continuously into the first of a series of compartments, so that liquid flows from the upper part of the first compartment and then through each of the remaining compartments, passing carbonic acid gas through the liquid in each compartment and collecting the white lead which is carried by the liquid leaving the last compartment. l i

6. Process for the manufacture of white lead, which consists in suspending lead oxid in water containing an assisting agent and 25 kept in continuous flow, passing carbonating gas through the suspension, and collecting the white lead carried awayon the sur-' face of the liquid. f

7. Process for the manufacture of white lead, which consists in suspending lead oxid in water containing an assisting agent and kept in continuous flow and at a raised temperature, passing carbonating gas through the suspension, and collecting the white lead carried away on the surface of the liquid.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

FREDERICK HERBERT SHARPE. [L. s.] 

